This invention relates generally to agricultural balers and, in particular, to such balers typically referred to as "round balers" which form cylindrical bales of crop material.
Three basic types of bale forming elements have been used in round balers. These are chain and slat aprons, belt aprons and rollers. Each type of bale forming element has advantages and disadvantages. For example, an advantage of chain and slat aprons is that they are capable of starting bales in almost all crop conditions but a disadvantage of these aprons is that they often form bales with rough outer surfaces. An advantage of belt aprons is that they form bales with smooth outer surfaces but a disadvantage of belt aprons is that they have bale starting problems in certain crop conditions. Rollers also have the advantage of forming bales with smooth outer surfaces but they have a disadvantage of resulting in losses of crop material through the gaps between adjacent rollers.
Copending U.S. patent application Ser. No. 063,390 of Richard E. Jennings, filed June 18, 1987 now U.S. Pat. No. 4,771,595 granted Sept. 20, 1988 and assigned to the same Assignee as this application, discloses a round baler utilizing a combination of bale forming rollers and a belt apron. In the disclosed round baler, the rollers are fixed and cooperate with the belt apron to define a generally D-shaped bale starting chamber. The fixed rollers form a front wall of the starting chamber, and the belt apron has an expandable course that forms a rear wall of the starting chamber. While the round baler disclosed in U.S. patent application Ser. No. 063,390 functions adequately in hay and when making full size bales, it encounters problems operating in straw and silage and when making less than full size bales. For example, the D-shaped starting chamber results in the generation of fines and causes the less than full size bales to be out-of-round and have lower than desirable density and poor appearance.
It is an object of the present invention to provide a round baler which incorporates as many advantages as possible of the three basic types of bale forming elements while minimizing the disadvantages thereof.
It is another object of the present invention to provide a round baler which overcomes the aforementioned problems encountered by the round baler disclosed in U.S. patent application Ser. No. 063,390.